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Does atrazine really have any benefit?

Do atrazine and its triazine cousins have any value to Cornbelt farmers? After all, the EPA is continually in a process of re-registering its use, even though approval might have just been certified. A recent estimate of the value of triazine products puts their value at $3 billion per year to agriculture, spread across the Cornbelt, and extending into sorghum and sugar cane regions of the US.

Your predecessors on your farm first began using atrazine in 1959, and it was the most widely used herbicide until recently overtaken by glyphosate. Numerous studies have been made of atrazine and its chemistry, the most recent study by agricultural economist Paul Mitchell of the University of Wisconsin. Mitchell’s study takes into account current corn production data, left out of prior reports, along with the economic impact of genetically modified corn and the increased dependence of the biofuel industry on corn. Mitchell adds that the recent issues surrounding glyphosate resistance in a dozen weed species increase the potential importance of atrazine as an alternative means of weed control.

Using all of these dynamics, Mitchell sets up a series of scenarios with and without the availability of atrazine to farmers and calculates the financial difference. For example he says if glyphosate is applied to 75% of corn acres, that would likely increase to as much as 100% if atrazine were not available.

Mitchell says one indicator of the value of atrazine is its widespread use, resulting from its low cost and effectiveness against many broadleaf weeds and grasses. He said USDA data indicated atrazine was used on 62% to 75% of corn acres between 1990 and 2005, declining only because of the introduction of glyphosate for corn. He says even when glyphosate was being applied to 75% of corn acreage in 2009, atrazine was being used on 57% of corn acres. Prior to glyphosate for corn, when 68% of acres were being treated with atrazine in 1991, the second most popular herbicide metolachlor was being used on only 20% of acreage.

If atrazine were unavailable for use, Mitchell says alternatives would be used and he based his value calculations on weed infestations, potential yield losses, herbicide efficacies, and crop potential in the various USDA production regions of the US. Based on yield data from other researchers, Mitchell computed a 20% yield loss without atrazine. Evaluating earlier reports, he said costs of additional herbicides were included, but not the time and machine cost of additional applications of herbicides. And he says because each field and farm are different, the cost is difficult to determine.

Examining the value of the weed control benefits, Mitchell used market price and input cost data from USDA from 2007 to 2009. For example, Mitchell uses the USDA’s Heartland Region, which is the central part of the Cornbelt, and says without atrazine, revenue losses would range from $31 to $36 per acre. He calculated that at $9,000 to $10,000 per farm based on only 281 acres of corn per farm, for a total of $2.2 to $2.7 billion for the four state heartland region. Losses in the other regions are millions of dollars per year and account for 25% to 30% of all US losses.

For those 281 acres of corn, described as average for Cornbelt farms, Mitchell says without atrazine, herbicide costs would be $750 or $177 million per year. The impact on net income in the Heartland region is about $10,000 per year, but when all US agricultural regions are tabulated, the net income loss climbs above $2.36 billion. With the loss of yield from the lack of atrazine, Mitchell says the average per acre revenue in his 2007 to 2009 period would be $547 using ERS data and $616 using NASS data. When combining income loss from corn, sorghum, sweet corn and sugar cane, Mitchell says the total would range from $3.0 to $3.3 billion per year, with 60% of the benefit in the Heartland region. He is quick to note that because current crop prices are 33% higher than in the 2007 to 2009 period, benefits would be increased by 33%.

Mitchell also looked at other benefits, which included the way atrazine enhanced the performance of other herbicides. Using the research of a number of weed scientists, he reports:1) Atrazine enhances the broadleaf spectrum of bromoxynil, and it complements the grass, control of acetochlor, where atrazine provides the broadleaf control.2) Atrazine enhances the broadleaf weed control value of other less efficacious herbicides and complements the efficacy of grass herbicides, which generates economic benefits for crop farmers.3) Atrazine cannot be used on soybeans, but by providing effective weed control in corn, atrazine reduces the weed seed bank and subsequent interference pressure from weed species that can be difficult to control in soybeans.4) Atrazine improves herbicide-resistant weed management by providing a low cost and effective alternative mode of action to glyphosate and other non-triazine herbicides in corn.5) Maintaining the availability of atrazine as an alternative mode of action is particularly important for herbicide resistance management since no new herbicide modes of action have been released for agronomic grain crops since 1990.

The Wisconsin economist found that the development of herbicide resistant weeds is a major concern of farmers, and reported that half of corn, soybean, and cotton farmers express that as their primary concern. He says based on current plantings, “if 5% more corn and soybean farmers became concerned about weed resistance because triazine herbicides were not available, these average per acre reductions in value imply an annual average loss of almost $15 million for corn farmers and almost $12 million for soybeans farmers, just from an increase in concern about herbicide-resistant weeds.” And he said that dollar value would double if the percentage of concern was doubled.

Another benefit identified by Mitchell is that of the environmental impact of reduced tillage, which cuts soil erosion by $44 billion annually and use of pesticides by $8 billion annually. With the effectiveness of atrazine in reduced till acreage, Mitchell says research found, “Every year, conventional tillage corn had the lowest percentage of acres using atrazine and no-till corn had the highest percentage, except in 2007 when a greater percentage of conservation tillage corn acres received atrazine than no-till acres. These data demonstrate that in corn production, atrazine is consistently used more often in reduced tillage systems than in conventional tillage systems.” Due to the increasing amount of weeds resistant to glyphosate, Mitchell says the use of atrazine becomes even more important in reduced tillage crops. Otherwise there would be a reversal of a 30 year trend in tillage reduction, just for control of glyphosate resistant weeds, if atrazine were not available.

Summary:Atrazine has become a mainstay of many farmers for broadleaf and grass control in corn, even with the use of glyphosate. It has been both a complement and a replacement for glyphosate, particularly in reduced tillage fields. However, benefits allowed by the use of atrazine can exceed $3 billion per year due to increased weed control that allows increased yield. This is not only true in the Cornbelt, but also benefits sorghum, sweet corn, and sugar cane production areas.